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Computation of Atmospheric Concentrations of Molecular Clusters from ab initio Thermochemistry
Published on: April 8, 2020
Response properties with explicitly correlated coupled-cluster methods using a Slater-type correlation factor and
Matthias Hanauer1, Andreas Köhn
1Institut für Physikalische Chemie, Universität Mainz, D-55099 Mainz, Germany. hanauem@uni-mainz.de
The Journal of Chemical Physics
|October 2, 2009
Summary
This study validates a new coupled-cluster method for calculating molecular properties. The explicitly correlated coupled-cluster (CCSD(F12)) model with cusp conditions accurately predicts electrical properties and optical rotations.
Area of Science:
- Quantum Chemistry
- Computational Chemistry
- Theoretical Chemistry
Background:
- Accurate calculation of molecular properties is crucial in chemistry.
- Explicitly correlated coupled-cluster methods offer improved convergence.
- The coupled-cluster ansatz with cusp conditions is a recent development.
Purpose of the Study:
- To assess the suitability of the extended explicitly correlated coupled-cluster ansatz with cusp conditions for response property calculations.
- To evaluate the accuracy of the CCSD(F12) model for static and dynamic electrical properties, including hyperpolarizabilities and optical rotations.
- To investigate the impact of basis set size and method simplifications on computational efficiency and accuracy.
Main Methods:
- Application of the explicitly correlated coupled-cluster ansatz with cusp conditions (CCSD(F12)).
- Computation of static and dynamic electrical properties, including electric second harmonic generation (ESHG) hyperpolarizabilities.
- Calculation of optical rotations.
- Utilized augmented quadruple zeta basis sets and explored an extension for reducing one-electron basis set error.
- Tested a simplified method-specific Lagrangian and examined the effect of triple and quadruple excitations.
Main Results:
- Effectively converged correlation contributions for response properties were reliably obtained using augmented quadruple zeta basis sets.
- The CCSD(F12) model with cusp conditions demonstrated suitability for calculating static and dynamic electrical properties and optical rotations.
- An optional extension effectively reduced the one-electron basis set error.
- A simplified Lagrangian proved uncritical for computational accuracy.
- Conventional triple and quadruple excitations were found to have a manageable impact in explicitly correlated calculations.
Conclusions:
- The extended explicitly correlated coupled-cluster ansatz with cusp conditions is a reliable method for computing molecular response properties.
- The CCSD(F12) model, even with augmented quadruple zeta basis sets, provides accurate results, reducing the need for larger basis sets.
- Methodological simplifications and extensions offer pathways to improve computational efficiency without compromising accuracy.
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